<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta http-equiv="X-UA-Compatible" content="IE=edge">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Document</title>
</head>
<body>
  <script>

// 封装函数
  function changeNum(a , b){
    let temp =0 
    temp = a
    a = b
    b = temp
    return`${a},${b}`
    
  }

// 调用函数
 let res = changeNum(1 , 2)
 console.log(res);
  </script>
</body>
</html>